// Store-release doesn't require store-load ordering.
(AtomicStoreRel32 ptr val mem) => (MOVWatomicstore ptr val mem)

// Atomic adds.
(AtomicAdd32 ptr val mem) => (AddTupleFirst32 val (LAA ptr val mem))
(AtomicAdd64 ptr val mem) => (AddTupleFirst64 val (LAAG ptr val mem))
(Select0 <t> (AddTupleFirst32 val tuple)) => (ADDW val (Select0 <t> tuple))
(Select1     (AddTupleFirst32   _ tuple)) => (Select1 tuple)